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Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light

par Aydogan, Akin;Bangle, Rachel;Cadranel, Alejandro;Turlington, Michael M.D.;Conroy, Daniel D.T.;Cauet, Emilie ;Singleton, Michael M.L.;Meyer, Gerald John;Sampaio, Renato R.N.;Elias, Benjamin ;Troian Gautier, Ludovic
Référence Journal of the American Chemical Society, 143, 38, page (15661-15673)
Publication Publié, 2021-09

Article révisé par les pairs

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Résumé :

Efficient excited-state electron transfer between an iron(III) photosensitizer and organic electron donors was realized with green light irradiation. This advance was enabled by the use of the previously reported iron photosensitizer, [Fe(phtmeimb)2]+ (phtmeimb = {phenyl[tris(3-methyl-imidazolin-2-ylidene)]borate}, that exhibited long-lived and luminescent ligand-to-metal charge-transfer (LMCT) excited states. A benchmark dehalogenation reaction was investigated with yields that exceed 90% and an enhanced stability relative to the prototypical photosensitizer [Ru(bpy)3]2+. The initial catalytic step is electron transfer from an amine to the photoexcited iron sensitizer, which is shown to occur with a large cage-escape yield. For LMCT excited states, this reductive electron transfer is vectorial and may be a general advantage of Fe(III) photosensitizers. In-depth time-resolved spectroscopic methods, including transient absorption characterization from the ultraviolet to the infrared regions, provided a quantitative description of the catalytic mechanism with associated rate constants and yields.